DEFINITION: A jerking that follows the engine speed, and is usually more pronounced when the engine load increases. The condition is not normally felt above 1,500 RPM, or 48 km/h (30 mph).

Preliminary Check

Refer to Symptoms - Engine Controls .

Ignition System Checks

Check for a cylinder misfire:

1. Start the engine.
2. Allow the engine to stabilize.
3. Disconnect the idle air control (IAC) motor.

Notice: Do not perform this test for more than 2 minutes in order to prevent damaging the catalytic converter.

4. Perform the Cylinder Power Balance Test with a scan tool.
5. If there is a RPM drop on all cylinders, equal to within 50 RPM, refer to Rough, Unstable, or Incorrect Idle and Stalling .
6. Reconnect the IAC motor with the ignition OFF.
7. If there is no RPM drop on one or more of the cylinders, or if excessive variation in drop occurs, check for spark on the suspected cylinders with a J 26792 Spark Tester or equivalent.
8. If there is no spark, refer to Distributor Ignition (DI) System Diagnosis .
9. If there is spark, remove the spark plugs in these cylinders and check for the following conditions:

•	Insulation cracks

•

Wear

•	Improper gap

•	Burned electrodes

•	Heavy deposits

10. Check the spark plug wire resistance. The resistance should not exceed 30,000 ohms.
11. Check the distributor rotor and the distributor cap.
12. If the previous check did not find the problem, visually check the following items:
13. Check the ignition system for the following items:

•

Moisture

•

Dust

•

Cracks

•	Burns, etc.

14. With the engine running, spray the plug wires with a fine water mist in order to check for shorts.
15. Perform the Fuel Injector Balance Test. Refer to Fuel Injector Balance Test with Tech 2 .

Engine Mechanical Checks

Fuel System Checks

Additional Check